It sounds like a relay operating (click). If you do not hear the hydraulic pump motor running it could be several things from dirty/corroded connections to an open winding on the motor.
Find the relay, (follow the click) check for voltage in and out, check the connections, (don't just look, remove, clean, replace)
There may be fuses at the motor, there are several in ours, which is a bit newer so it may be different. When our slides quit (same motor as jacks) the problem was an intermittent winding on the motor. Had to get the assembly replaced.
Good luck and please let us know what you find.